TABLE 2.
Relative affinities of IL-21 variants to IL-21Rα determined in ALPHAscreen competition test
Increasing concentrations of IL-21 variants were added to compete the binding of biotinylated wt IL-21 to IL-21Rα-His6. The relative affinities of IL-21 variants to IL-21Rα is expressed by the IC50mut/wt value. Values of IC50mut/wt greater than one indicate decreased binding affinity by the variants toward IL-21Rα relative to wt IL-21. IC50 values were measured in three independent experiments. mut, IL-21 variants.
| Alanine variant | IC50mut/wt ± S.D. | Charge variant | IC50mut/wt ± S.D. |
|---|---|---|---|
| M7A | 1.2 ± 0.2 | M7D | 2.1 ± 0.2 |
| R11A | 0.5 ± 0.1 | R11D | 13.0 ± 1.3 |
| I14A | 2.5 ± 0.2 | I14D | 97.0 ± 4.1 |
| D18A | 13.2 ± 0.5 | D18K | 15.9 ± 1.5 |
| E100A | 0.9 ± 0.1 | E100R | 23.2 ± 2.7 |
| E109A | 2.3 ± 0.3 | E109R | 20.1 ± 2.7 |
| S113A | 1.2 ± 0.2 | S113D | 2.3 ± 0.3 |
| Q116A | 0.9 ± 0.1 | Q116D | 0.9 ± 0.1 |
| K117A | 3.9 ± 0.4 | K117D | 7.1 ± 0.8 |
| I119A | 5.7 ± 0.4 | I119D | 27.1 ± 1.9 |
| H120A | 1.0 ± 0.1 | H120D | 0.3 ± 0.0 |
| L123A | 0.8 ± 0.2 | L123D | 0.4 ± 0.1 |
| WT | 1.0 ± 0.1 |